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Methane oxidation coupled to nitrate reduction under hypoxia by the G ammaproteobacterium M ethylomonas denitrificans , sp. nov. type strain FJG1
Author(s) -
Kits K. Dimitri,
Klotz Martin G.,
Stein Lisa Y.
Publication year - 2015
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12772
Subject(s) - biology , paracoccus denitrificans , denitrification , verrucomicrobia , anaerobic oxidation of methane , operon , aerobic denitrification , methanotroph , microbiology and biotechnology , nitrite reductase , biochemistry , nitrate , proteobacteria , nitrate reductase , denitrifying bacteria , gene , nitrogen , ecology , chemistry , enzyme , escherichia coli , 16s ribosomal rna , organic chemistry , catalysis
Summary Obligate methanotrophs belonging to the Phyla Proteobacteria and Verrucomicrobia require oxygen for respiration and methane oxidation; nevertheless, aerobic methanotrophs are abundant and active in low oxygen environments. While genomes of some aerobic methanotrophs encode putative nitrogen oxide reductases, it is not understood whether these metabolic modules are used for NO x detoxification, denitrification or other purposes. Here we demonstrate using microsensor measurements that a gammaproteobacterial methanotroph M ethylomonas denitrificans sp. nov. strain FJG1 T couples methane oxidation to nitrate reduction under oxygen limitation, releasing nitrous oxide as a terminal product. Illumina RNA ‐Seq data revealed differential expression of genes encoding a denitrification pathway previously unknown to methanotrophs as well as the pxmABC operon in M . denitrificans sp. nov. strain FJG1 T in response to hypoxia. Physiological and transcriptome data indicate that genetic inventory encoding the denitrification pathway is upregulated only upon availability of nitrate under oxygen limitation. In addition, quantitation of ATP levels demonstrates that the denitrification pathway employs inventory such as nitrate reductase NarGH serving M . denitrificans sp. nov. strain FJG1 T to conserve energy during oxygen limitation. This study unravelled an unexpected metabolic flexibility of aerobic methanotrophs, thereby assigning these bacteria a new role at the metabolic intersection of the carbon and nitrogen cycles.